1. Field of the Invention
The present invention relates to an air vent plug arrangement for clean container and, more particularly, to an air vent plug arrangement for use in a clean container, for example, a wafer carrier, reticle container, or the like to keep the inside air pressure of the clean container in balance with the atmospheric pressure, and allow the clean container to breathe through the filtered air vent, minimizing the amount of unfiltered air that leaks through the door seal.
2. Description of Related Art
A regular wafer carrier or reticle container is adapted to transport wafers or reticles between a stocker and a load port or opener. A conventional clean container for this purpose has an access opening and a door panel adapted to close the access opening. It is not easy to disconnect the door panel from the access opening because of a sealer between them. When directly opening the door panel, a flow of air may rush into the inside of the clean container, causing storage wafers or reticles to be contaminated with particles or pollutant carried in the flow of air. There is known another design of a clean container, which comprises a blocking block adapted to seal the air vent in the lining of the door panel thereof, and a linkage controlled by a latch key to move the blocking block from the air vent for circulation of air to keep the inside air pressure and the outside air pressure of the clean container in balance. This design still has numerous drawbacks. Because the air vent is provided in the lining of the door panel, it is not easy to dismount the internal structure of the door panel during a repair work. If a filter is used, the replacement of the filter is difficult to achieve. Due to limited space, the design of the position and size of the air vent is restricted. Also, particles caused by the abrasion of the mechanisms will reduce the airflow capability and life of the filter.
Therefore, it is desirable to provide an air vent plug arrangement for a clean container that eliminates the aforesaid drawbacks.
It is the main object of the present invention to provide an air vent plug arrangement for clean container, which is easy to mount and dismount. It is another object of the present invention to provide an air vent plug arrangement for clean container, which keeps the inside air pressure and outside air pressure of the clean container in balance rapidly, and allows the clean container to breathe through the filtered vent, minimizing the amount of unfiltered air that leak through the door seal.
To achieve these and other objects of the present invention and according to one aspect of the present invention, the air vent plug for clean container comprises an air ventilation plug arrangement installed in an air vent of a clean container, comprises a mounting ring, a plug body, and a plug cap. The mounting ring is fixedly fastened to the air vent of a clean container, the mounting ring comprising an inner surface, an outer surface, a bottom side edge, and at least two pegs symmetrically provided at the outer surface. The plug body is shaped like a cap, comprising a top sidewall, an annular peripheral sidewall, a collar extended outside around the annular peripheral sidewall on the middle and dividing the annular peripheral sidewall into an upper part insertable into the inside of the inner surface of the mounting ring, and a lower part, and at least two hooks symmetrically axially extended from the lower part. The plug cap is adapted to secure the plug body to the mounting ring, comprising a bottom sidewall, an outer ring upwardly extended from an outer diameter of the bottom sidewall and fitted over the outer surface of the mounting ring, an inner ring upwardly extended from an inner diameter of the bottom sidewall and fitted into the annular peripheral sidewall of the plug body, at least two top hooks respectively extended from the outer ring and hooked on the at least two pegs of the mounting ring, a top sidewall integral with a top side of the inner ring of the plug cap, and at least two retaining notches disposed in the inner ring adjacent to the bottom sidewall and forced into engagement with the at least two hooks of the plug body respectively. During installation, the inner ring of the plug cap is inserted into the plug body to force the respective retaining notches into engagement with the respective hooks of the plug body, and then the upper part of the plug body is inserted into the mounting ring, and then the plug cap is rotated through an angle to force the hooks of the plug cap into engagement with respective pegs of the mounting ring.
According to another aspect of the present invention, the air vent can be formed in the bottom panel, top panel, side panel, or door panel of the clean container. Preferably, the air vent is provided at a broad area adjacent to the access opening of the clean container, so that the diameter of the air vents can be made as big as possible for enabling the inside air pressure and the outside air pressure to be rapidly in balance.
According to still another aspect of the present invention, an O-ring is mounted outside the upper part of the annular peripheral sidewall of the plug body and stopped between a collar of the plug body and the bottom edge of the mounting ring for sealing, and a filter is mounted inside the plug body to prevent airborne particles from entering the clean container during air pressure equalization.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.